Add EPSS score to vulnerability report

What does this MR do and why?

• Adds CVSS and EPSS to graphQL query. (Note only EPSS is being consumed in the frontend in this MR, but we are adding CVSS to the query because it will be used soon)
• EPSS and CVSS fields already exist in graphQL backend. They were recently added.
• Backend is not currently feeding data to the fields, the frontend work is ahead. So we hide the value it's not defined.

References

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Screenshots or screen recordings

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Before	After

How to set up and validate locally

• Go to a project with vulnerabilities
• Observe that the vulnerability report page renders fine, without errors
• You will not see EPSS score appear, because backend doesn't currently populate the field. We hide it if it isn't defined.
• Screenshots used mocked data, but same API.

Related to #497388 (closed)